In methods for obtaining images by electrophotographic printing and electrostatic charge development, an electrostatic charge image formed on a photosensitive body is developed by toner which has been previously charged by friction, and then fixed. Fixing systems include heat roller systems wherein the toner image obtained by development is fixed using a pressurized or heated roller, and noncontact fixing systems wherein fixing is accomplished using an electric oven or a flash of light. In order to carry out the process in a successful manner, the toner must first hold a stable charge, and must secondly have a satisfactory property of fixing onto paper. In addition, as the apparatus has a heated fixing member which increases the temperature inside the apparatus, the toner must also be resistant to blocking. Recently, with the increased compactness of fixing members in heat roller systems, rollers are being employed that are not coated with release agents such as silicone oil. This has produced a high demand for toners with releasability from heat rollers, also known as a non-offset property. Also, recently, in demand are toners capable of forming glossy images, as full color electrophotographic systems come into wider use.
Toner binder resins, which have a major influence on the above-mentioned toner properties, include polystyrene resins, styrene-acryl resins, polyester resins, epoxy resins, polyamide resins and the like, and particular attention has been focused on polyester resins for their ability to achieve a satisfactory balance between transparency and fixing property, as well as their superior transparency and general suitability for full color toners.
However, toners using polyester-based resins as the binder resins tend to have a lower non-offset property than other resins such as styrene-acryl resins, while it has also been difficult to simultaneously achieve sufficient gloss.
One problem, for example, has been that enhancing the non-offset property of a toner by increasing the polymer weight or elasticity of the binder resin also lowers the gloss of the resulting image.
Moreover, it has not been possible to obtain adequate effects because release agents added to toners are not readily uniformly miscible in the binder resins.